Synaptonemal complex formation and meiotic checkpoint signaling are linked to the lateral element protein Red1.

Meiosis generates four haploid daughters from a diploid parental cell. Central steps of meiosis are the pairing and recombination of homologous chromosomes followed by their segregation in two rounds of cell division. Meiotic recombination is monitored by a specialized DNA damage checkpoint pathway and is guided by a unique chromosomal structure called synaptonemal complex (SC), but how these events are coordinated is unclear. Here, we identify the SC protein Red1 as a crucial regulator of early meiosis. Red1 interacts with two subunits of the 9-1-1 checkpoint complex via two distinct 9-1-1 subunit-specific motifs. Association of 9-1-1 with Red1 is essential not only for meiotic checkpoint activation but for SC formation. Moreover, Red1 becomes SUMO-modified, which fosters interaction of Red1 with the central SC element Zip1, thereby securing timely SC formation. Thus, Red1, in addition to its structural role in the SC, is a crucial coordinator of meiosis by coupling checkpoint signaling to SC formation.